Grotto No.419 and Grotto No.420 of the Mogao Grottoes in Dunhuang were excavated in Sui Dynasty, when Buddhism of the Sui developed to its zenith.No.419 depicts the actual transformations of the buddhas and No. 420 is more a symbolic manifestation of this transformation.Two different sects of the Buddhist thoughts intertwine in the pictures of Grottos No.420:the Saddharma-pundarika sutra and the nirvana sutra,which indicates that both were flourishing in the Sui Dynasty although the former seems to overwhelm the latter.With reference to previous studies,the author maintains that this is part of the scriptures of the Universal Gate.All the pictures in Grottos No.419 show that they were evolved from the traditional started by Kumarajive.The paper further shows,with substantial examples,that the two sects worked together to contribute to the artistic merits of the two grottoes.